RAVENA -- The state has given air and water pollution permits needed for the planned rebuilding of the Lafarge cement plant in Ravena.

The permits, issued this week by the state Department of Environmental Conservation, clear the way for Lafarge to build a less-polluting, modern plant to replace its current 49-year-old plant off Route 9W.

That new plant is expected cost several hundred million dollars and to be running by 2015; the new permits run through September 2015.

The permits reflect a change in the way cement will be made, from a current "wet" kiln process, that uses water with a mix of limestone, coal fly ash and other materials, to a less energy-intensive "dry" process where water is not used.

"By transforming the Ravena plant into the most advanced cement facility in New York state, we will remain competitive for the long term, protect good paying jobs, and significantly cut plant emissions," said plant manager Martin Turecky,

While cement production at the new plant is expected to increase by up to two-thirds, the amount of toxic mercury emissions are expected to drop by two-thirds, said DEC Commissioner Joe Martens.

Currently, Lafarge is the state's second-largest source of airborne mercury pollution. The plant's air pollution permit was renewed last year amid scrutiny by grassroots activists who want less air pollution from Lafarge.

Mercury is a potent neurotoxin that can cause developmental problems in children and fetuses. The metal can pass from pregnant women to their fetuses.

A recent study by researchers from Harvard University of about 170 residents who live around the plant found that one in 10 had mercury levels elevated enough to warrant a visit to the doctor. Study participants still have not received individual results, which are being reviewed by the state Health Department.

Current air pollution permits allow Lafarge to emit up to 176 pounds of mercury a year. The new plant would be allowed to emit no more than 59 pounds.

Other pollutants will also decrease at the new plant, according to Martens.

Emissions of sulfur dioxide, a gas that causes acid rain, will drop 95 percent, or about 11,200 tons a year and nitrofent sulfides, which cause smog, will decline by almost two-thirds, or about 3,100 tons a year.

Also, the emission of fine airborne particles will drop from 560 tons annually to 351 tons. The new plant will no longer discharge used water back into the Hudson River, and the amount of water taken from the river for manufacturing purposes will drop by 75 percent, from eight million gallons a day to no more than 2 million gallons a day. Most of the water used in manufacturing will come either from the limestone quarry or wells that Lafarge has on the property.

The current 325-foot smokestack would be replaced by a 525-foot "preheater/precalciner tower."